Warping in Cryo

M

Mike Read

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Mar 27, 2015
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I am planning to start cryo treating my blades and would like to know if they are likely to warp at all during the Cryo soak.

I am using RWL34 mostly and plate quench which keeps them pretty straight. I grind bevels after heat treat.

If I just lower my blades into nitrogen are they likely to warp?

Should I clamp them between plates before putting them into cryo?

If I dont need to clamp the blade I can use a narrow neck dewar which holds for longer, otherwise I will try and find one with a wide neck.

Any advice appreciated.

Thanks

Mike
 
A while back I did 2 blades out of Lc 200n. One of them I did a sub-zero and this blade was fine after the sub-zero but warped pretty bad during temper(450F).I,m clamping mine from now on.Didn't have this problem with Aebl tho. I grind hard also. Hope my limited experience helped.Good luck. Lu.
 
I've had them warp a little in dry ice and kerosene, but that was before I started grinding after HT. When you grind bevels and tapered tangs, then try to plate quench, all bets are off as far as warpage goes, in my experience. Lately I've had no problems, and that's using alot of 3/32 thick steel.
 
If you have warping it means one or more of your HT steps has been done wrong. I remember one maker had , as a last step, put the blade side down on the bottom of the cryo container !! You can suspend the blade above the LN or in the LN but don't lay it down on it's side .Cryo takes perhaps 4 hours !
 
Hi Mete,my warping occurred after tempering.( It was fine after the sub-zero.)Would clamping the blade help during tempering or would there be memory in the steel to warp again after the clamp was removed? On a side note I followed the manufacturers heat treat to the letter. Also I grind post heat treat.Thanks Lu.
P.S steel was Lc 200n.
 
mete said:
If you have warping it means one or more of your HT steps has been done wrong. I remember one maker had , as a last step, put the blade side down on the bottom of the cryo container !! You can suspend the blade above the LN or in the LN but don't lay it down on it's side .Cryo takes perhaps 4 hours !
Click to expand...

I havent had any warping since I started plate quenching and grinding hard. The Cryo is just an unknown at the moment as I have no experience of it.

So far it sounds like warping in cryo is unlikely.

All comments appreciated.

Are there any makers who clamp up their blades for cryo?

Thanks

Mike
 
Lu1967, how do you temper? As any other ht step, the temperature should be even inside the piece; if you draw one side more then the other the blade will warp.
That applies to LN too, and also to any other thermal treatment.

And... steel has no memory; it has microstructure. Our goal is to manipulate the steel's microstructure with heat treatments to have it omogeneous and refined.
 
Last edited:
Hi stezann,I temper in an old household oven lined with fire bricks and the blades are left flat in a foil pan.It takes about an hour for the temp to equalize.
The blade remained flat after my sub-zero but warped after the temper.(steel was Lc200n)I did 2 of the same blades except 1 received no sub-zero, and that one was fine.(warped a tiny tiny bit)I think I will clamp during the temper with some precision ground flat stock. (these are blanks,I grind hard) I hope this does the trick ( unless flatstock decides to do something weird ugh) Thanks again Lu
 
Lu, I'm guessing yours warped because they were left flat in the pan. Set them on their spines and I suspect they'll stay straight.
 
Make a tempering rack from a couple fire soft bricks and stainless rods stuck in them, spaced every 1/2". Set two in the oven and place the blades standing on their spine between them.
 
also i suggest to have the blades in a rack, an be sure the oven equalizes before putting the blades into it.
 
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